Thermoreversible hydrogels X: Synthesis and swelling behavior of the (N-isopropylacrylamide-co-sodium 2-acrylamido-2-methylpropyl sulfonate) copolymeric hydrogels

A series of thermosensitive hydrogels were prepared from various molar rati os of N-isopropylacrylamide (NIPAAm) and sodium-2-acrylamido-2-methylpropyl sulfonate (NaAMPS). Factors such as temperature and initial total monomer concentration and different pH solutions were investigated. Results indicat ed that the more the NaAMPS content in hydrogel system, the higher the swel ling ratio and the gel transition temperature; the higher the initial monom er concentration, the lower the swelling ratio. The result also indicated t hat the NIPAAm/NaAMPS copolymeric hydrogels had different swelling ratios i n various pH environments. The present gels showed a pH-reversible property between pH 3 and pH 10 and thermoreversibility. The swelling ratios of cop olymeric gels were lower in a strong alkaline environment because the gels were screened by counterions. Finally, the drug release behavior of these g els was also investigated in this article. (C) 2000 John Wiley & Sons, Inc.